The subject matter disclosed herein generally relates to heat exchangers and, more specifically, to alloys for finned heat exchangers.
Heat exchangers are widely used in various applications, including but not limited to heating and cooling systems including fan coil units, heating and cooling in various industrial and chemical processes, heat recovery systems, and the like, to name a few. Many heat exchangers for transferring heat from one fluid to another fluid utilize one or more tubes through which one fluid flows while a second fluid flows around the tubes. Heat from one of the fluids is transferred to the other fluid by conduction through the tube walls. Many configurations also utilize fins in thermally conductive contact with the outside of the tube(s) to provide increased surface area across which heat can be transferred between the fluids, improve heat transfer characteristics of the second fluid flowing through the heat exchanger and enhance structural rigidity of the heat exchanger. Such heat exchangers include microchannel heat exchangers and round tube plate fin (RTPF) heat exchangers.
Heat exchanger tubes may be made from a variety of materials, including metals such as aluminum or copper and alloys thereof. Aluminum alloys are lightweight, have a high specific strength and high-heat conductivity. Due to these excellent mechanical properties, aluminum alloys are used as heat exchangers for heating or cooling systems in commercial, industrial, residential, transport, refrigeration, and marine applications. However, aluminum alloy heat exchangers have a relatively high susceptibility to corrosion. Corrosion eventually leads to a loss of refrigerant from the tubes and failure of the heating or cooling system. Sudden tube failure results in a rapid loss of cooling and loss of functionality of the heating or cooling system. Many aluminum alloys are of course known, each having a relative susceptibility or resistance to corrosion. However, many alloys reported to have relatively high resistance to corrosion may not have desired physical properties for use as heat exchanger fins or may not have desired formability characteristics for fin fabrication and assembly with heat exchanger tubes or channels. For example, conventional anodic aluminum alloys such as alloy 7072 suffer from limitations on formability, which is particularly problematic for heat exchangers having low fpi (fins per inch) counts, with correspondingly high collar dimensions. For some heat exchanger designs with lower fpi counts, 7072 fins are subject to cracking and other defects at lower fpi counts due to 7072's limited formability. For such designs, 7072 is limited in the minimum fpi count that can be achieved.
In view of the above and other considerations, further contributions to the field of aluminum alloys for heat exchangers are well-received in the art.